The present invention relates to a gear shift mechanism for a manual transmission.
In a manual transmission, a sliding member, such as a sliding gear or a sliding coupling sleeve, in a gear train is axially moved in and out of mesh with another gear member. Such a shift operation is performed by a gear shift mechanism, which comprises a shift rod axially moved by a driver's manual input force and a shifter member which is moved by the shift rod movement and moves the sliding member in and out of mesh.
If such a shift rod is designed to move only a single sliding member through a single shifter member, it is advantageous to fix the shifter member to the shift rod. If, however, a shift rod moves in one direction to move one sliding member into its shift position through one shifter member and moves in the opposite direction to move another sliding member into its shift position through another shifter member, it is undesirable to fix the both shifter members to the shift rod. If the both shifter members are fixed to the shift rod, one shifter member must move from its neutral position toward the direction opposite to its shift position while the other shifter member is moved toward its shift position. This is disadvantageous to reduction in transmission size because there must be provided enough space for each sliding member to move in both directions from its neutral center.
In view of this, gear shift arrangements in which both the shifter members are not fixed to the shift rod have been proposed. One example of such arrangements is disclosed in Japanese published utility model application, examined publication No. 15878/1978. In this example, one (or both) of the two shifter members is not fixed to the shift rod but slidably mounted on the shift rod. This shift rod has a projecting portion for pushing the non-fixed shifter member from its neutral position to its shift position. There is provided, between the shift rod and this shifter member, an interlocking member which interlocks the shift rod and this shifter member thereby to cause this shifter member to return from its shift position to its neutral position. While the shift rod is moving in the opposite direction to move the other shifter member, the interlocking member is driven out of its interlocking position so that the former shifter member is not moved in the opposite direction by this shift rod movement but held stationary in its neutral position. Thus, the stroke of the shifter member is limited within the distance between its neutral position and its shift position.
In this arrangement, however, in order to hold the interlocking member, there must be formed in the shifter member a hub portion with which the shifter member is slidably mounted on the shift rod and which is long enough in the sliding direction to accommodate the interlocking member. Therefore, the shifter member can not be fabricated by blanking or other inexpensive method, but must be made by casting, forging or welding a main portion and a hub portion of a shifter member, which all increase the cost of the shifter member.